Size reduction of wireless power and data delivery systems is vital for the development of miniaturised wearable and implanted devices. In the design of implantable technology there is a worldwide drive towards minimally invasive surgical procedures (e.g. laparoscopic surgeries) which necessitates bioimplants with small dimensions. Certain prostheses also have significant geometrical constraints to properly conform to the targeted organs. Delivery of power and data to electronic medical prostheses has been demonstrated in a variety of devices, ranging from the high power consumption devices such as the cochlear implant (Clark, G., 2003, Springer Science & Business Media, New York, p. 459) and retina stimulators (Weiland, J. D. et al., 2005, Annu. Rev. Biomed. Eng. 7 (1), 361-401) to low power prostheses such as spinal cord stimulators (Cameron, T., 2004, J. Neurosurg. Spine 100 (3), 254-267) and cardiac pacemakers (Mallela et al., 2004, Indian Pacing Electrophysiol. J. 4(4), 201-212).
Photovoltaic (PV) cells used in solar panels and other applications convert light into electricity. Sunlight has a broadband spectrum, which yields a low spectral power density that is harvested less efficiently in PV cells. By contrast, a laser emits a collimated beam of light from which it is possible to extract substantially more electrical energy using a PV cell. Matching the photovoltaic cell technology to the wavelength of the incident laser light further improves efficiency. Visible (VIS), near infrared (NIR) and infrared (IR) wavelengths have been used to deliver therapeutic optical treatments in patients. NIR is of particular interest owing to its relatively long tissue penetration depth, and it has been used clinically for non-invasive imaging such as neuroimaging (G. Strangman, D. A. Boas, and J. P. Sutton, Biol. Psychiatry 52, 679 (2002)) and retina photodynamic therapy (U. Schmidt-Erfurth and T. Hasan, Surv. Ophthalmol. 45, 195 (2000)).
Higher power consumption prostheses in the tens of mW require power delivery from external sources. These devices also often require continuous power delivery. Typically these devices are powered wirelessly using inductively coupled coils of significant volume. It is known that the transmitted power of inductively coupled systems reduces rapidly with the reduction in size of the magnetic coil. The geometric constraints of the coils also means that they characteristically occupy large volumes in order to provide sufficient power to the implant and constitute a significant portion of the implant volume, or they are located away from the implant and connected to it with a permanent cable. In the case of a retinal implant, such limitations may require the placement of a permanent cable through the eye wall, thus requiring complex surgery and increasing the risk of complications. This is unlike a photovoltaic (PV) power receiver, where the power density is independent of the receiver volume. A PV receiver can maintain its power density regardless of the dimension. Ahnood et al. (Biosensors and Bioelectronics 77 (2016) 589-597) reported a PV power density in the range of 20 mW/mm3 which compares favourably with the coil based range of 0.01˜1.8 mW/mm3, and plays a key role for miniaturization implants. Therefore, PV power delivery is well suited for miniaturised implants.
Diamond capsules are stable in the body, are nontoxic, transparent, and are known for packaging of chronic implants. The wide transmission spectrum of diamond makes it suitable for use as an optical window for PV implants, while the inherent properties of the diamond, such as its mechanical robustness, biocompatibility (Bajaj et al. Biomed. Microdevices 9(6), 787-794, 2007; Tong et al., Mater. Sci. Eng. C43, 135-144, 2014), and chemical inertness (Zhou and Greenbaum, 2010, Implantable Neural Prostheses 2: Techniques and Engineering Approaches. Springer Science & Business Media, New York), make it ideal for use as a long lasting clinical implant. FIG. 1A illustrates a photovoltaic power/data receiver integrated within a diamond encapsulated implant and a diamond optical window tailored to maximise the captured light. FIG. 1B is an image of components of a miniaturised bioimplant as shown in Ahnood et al. (Biosensors and Bioelectronics 77 (2016) 589-597).
Diamond electrodes comprising a plurality of electrically conductive elements made from a nitrogen doped diamond material can also be electrically integrated in the bioimplant, as described in US2014/0094885. Thus, such a capsule and electrodes form an integrated diamond package eliminating any potential break in the seal at each electrode. In the absence of external wiring, the only seal in the capsule is the welding of the top and bottom halves of the capsule. The laser welding of a gold active brazing alloy (Au-ABA) for joining two diamond capsule halves to create a biocompatible, hermetically sealed joint has been demonstrated in Lichter et al. (Biomaterials 53, 464 (2015)). The biostability of gold active brazing alloy (Au-ABA) has been further assessed with the implantation of Au-ABA into the back muscle of pigs (Ahnood et al., Biosensors and Bioelectronics 77 (2016) 589-597), showing no corrosion after 12 weeks. The delivery of power and data to a self-contained implant without any external wiring calls for the encapsulation of the device microelectronics and of the PV cell in an optically transparent capsule, whose properties include hermeticity, biocompatibility and long term stability. Ahnood et al. (Biosensors and Bioelectronics 77 (2016) 589-597) have demonstrated the safe, compact and robust use of transdermal power delivery through photovoltaic cell technology. The PV cell delivered 20 mW/mm3 transdermally, whilst the diamond capsule remained stable in the tissue with no degradation over a period of 6 months in a guinea pig animal model. Although bare diamond reflects a significant portion of light, methods such as anti-reflective coating, surface texturing, and nanostructures can be used to virtually eliminate reflective losses, particularly for a targeted wavelength.
There remains a need for a system and method for transmission of power and data to a remote device from a collimated beam, wherein the device and the source apparatus may move with respect to each other within certain constraints.
This background information is provided for the purpose of making known information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention.